n.
Sum of all processes, chiefly chemical, that produce changes in a sediment after its deposition but before its final lithification .
Usually, not all the minerals in a sediment are in chemical equilibrium, so changes in interstitial water composition or in temperature or in both will lead to chemical alteration of one or more of the minerals present. Diagenesis is considered a relatively low-pressure, low-temperature alteration process that involves such processes as cementation, reworking, replacement, crystallization, and leaching.